The present invention relates to a process for producing electroconductive fibrous shaped-articles of which fibers thereof are subjected to metallizing plating, and more in detail, the present invention relates to a process for producing electroconductive fibrous shaped-articles of which the fibers constituting the shaped-articles are uniformly and firmly subjected to metallizing plating by chemically plating the fibrous shaped-articles after having colloidal palladium adsorbed thereonto uniformly and firmly.
Since the electroconductive fibrous shaped-articles which have been provided with electroconductivity by subjecting the fibrous shaped-articles made of paper and/or non-woven cloth to metallizing plating are lighter and less expensive than the metallic materials, the electroconductive fibrous shaped-articles are used as the material for electromagnetic shields, for preventing electrification of electronic parts such as IC and for electrostatic recording.
Although the fibrous shaped-articles made of paper and/or non-woven cloth are originally insulating materials, because the fibrous shaped-articles are lighter and cheaper than the metallic materials, the fibrous shaped-articles have been subjected to various processes of adhering several metals onto the fibrous shaped-articles, thereby providing electric properties such as electroconductivity and magnetic properties to the fibrous shaped-articles.
In this case of adhering a metal onto the fibrous shaped-articles, in order to retain the thus adhered metal stably for a long time, it is necessary that the metal is adhered to the fibrous shaped-articles as uniformly and firmly as possible, and it is demanded that the adhered metal hardly falls off on the occasion of contacting with a solid body.
The conventional process for producing such electroconductive fibrous shaped-articles comprises adhering an electroconductive powdery material such as metallic powder and/or carbon black onto the fibrous shaped-articles by using a suitable fixing agent (for instance, refer to Japanese Patent Application Laid-Open No. 57-183496 (1982)).
As the other process, there is a process wherein the fibers constituting the fibrous shaped-articles are coated with a metal, namely, a strong acidic palladium-tin colloid is adhered to the fibrous shaped-article and then the thus treated shaped-articles are subjected to electroless chemical plating, thereby obtaining the electroconductive paper (for instance, refer to German Patent No. 28 06 835).
The largest problem in the electroconductive fibrous shaped-articles according to the conventional process lies in the fact that the electroconductive powdery material or the electroconductive coating adhering to the shaped-article is apt to fall off therefrom easily on the occasion of the contact of the shaped-article with other solid bodies, particularly occurring on the outer surface of the shaped-articles.
Namely, according to the afore-mentioned process disclosed in Japanese Patent Application Laid-Open No. 57-183496 (1982), since the electroconductive powdery material only adheres on the surface of the fibrous shaped-article, it is apt to fall off on the occasion of the contact with other solid bodies. On the other hand, in the process disclosed in German Patent No. 28 06 835, it is difficult to uniformly adhere the metal on the fibrous shaped-articles, and the process has a demerit of more complicated steps.
The reason why it is difficult to uniformly adhere the metal on the fibrous shaped-articles lies in the fact that the strongly acidic palladium-tin colloid is not too stable and accordingly, the palladium-tin colloid begins to coagulate and precipitate after 3 to 4 months of the preparation of the colloid, and further the catalytic activity thereof is reduced in that period. In addition, the reason also lies in the fact that tin hydroxide disturbing the catalytic action other than palladium which acts as a catalyst in the chemical plating, is also adhered to the shaped-article in a large amount.
In order to remove impurities such as the tin hydroxide disturbing the catalytic action from the fibrous shaped-article, the fibrous shaped-article once soaked in the strongly acidic palladium-tin colloidal solution is further treated by soaking thereof in an aqueous alkaline solution. However, it is difficult to completely remove such impurities as tin hydroxide by such a procedure and such a procedure makes the steps more complicated.
Accordingly, it has been strongly demanded to offer a process for uniformly and firmly adhering the metal on the fibrous shaped-article by an extremely easy step.
In consideration of the present situation, as a result of the present inventors' studies for finding a process for providing electroconductivity to the fibrous shaped-articles, it has been found by the present inventors that by the use of a palladium hydrosol stabilized by a surfactant, it is possible to uniformly adsorb palladium into the water-absorptive fibrous shaped-article, and the fibers constituting the fibrous shaped-article can be metal-coated by chemically plating the fibrous shaped-article to which palladium has been uniformly adsorbed, and on the basis of the finding the present invention has been attained.